Actuators utilizing a voice coil and a magnet are known and have been in use for many years and in a wide array of applications. Due to the elementary physics principle that momentum in a closed system is conserved, movement of the voice coil from reaction to the opposing magnetic fields produces an equal and opposite reactionary force or recoil on the stationary body, in this example, the magnet. Likewise, in a grounded voice coil configuration, where the magnet moves and the voice coil is stationary, the recoil or reactionary force is imparted to the voice coil.
In sensitive equipment, for example computer disc drives and laser trimming equipment for electrical circuit resistors and capacitors, this recoil force, if not sufficiently dampened or otherwise managed, can become a problem and affect the accuracy of the principal device. For example, in laser trimming of electrical resistors or capacitors, the laser is typically used in combination with a highly sensitive measuring device to test the properties of the altered component. The laser and mirrors may be actuated by galvanometers in closed loop servo control systems to direct the laser to the desired area on the work piece. Rapid movement of the laser and mirrors causes momentum which, if not dampened or otherwise managed, could adversely affect the measurement device and compromise the accuracy of measurement. An example of a laser trimming device is Electro Scientific Industries, Inc. Model 2100 which is the assignee of the present invention.
The need to dampen the recoil force has long been sought after and many designs have attempted to eliminate or completely neutralize the recoil force with limited success. One past design is U.S. Pat. No. 5,146,122 for a Voice Coil Actuator with Resiliently Mounted Shorted Turn. In this design, an additional shorted turn component is introduced and placed in contact with the magnet to absorb recoil forces imparted on the magnet by a voice coil carriage. An alternate design is in U.S. Pat. No. 3,699,555 for an Apparatus for Rapid Action Displacement Control. In this design, the magnet/stator is mounted on roller bearings positioned on rods. The transducer carriage is mounted on wheels that ride on tracks.
These designs include additional complex precision components such as the shorted turn and require additional assembly steps which add cost and time to manufacture and assemble the device. Neither device includes a flexure as they incorporate bearings or isolators to dampen the recoil. Neither design is believed to produce a truly recoilless actuator.
Past designs that have employed dampeners or flexures on either the voice coil (in a magnet-grounded configuration) or on the magnet (in a voice coil-grounded configuration) in an attempt to reduce or eliminate the resultant recoil forces experienced by the grounding structure, do not produce a recoilless system with respect to the ground structure.
Therefore, there is a need for a method of operation and an actuator employing a flexure for both the magnet and the voice coil assemblies to substantially reduce or completely eliminate recoil forces previously experienced by the grounding structure to improve the performance of the actuator and the surrounding system or equipment.